The Rhine Estuary-Drechtsteden region is a densely populated area of immense economic significance to the Netherlands. It is an area of extremes: with port activities, urban areas, the Greenports (horticulture), and the Biesbosch nature reserve.
In this region – around Rotterdam and Dordrecht – water comes from two directions: the sea and the rivers. Economic and spatial development in the Rhine Estuary-Drechtsteden region is only possible if its flood protection , its freshwater supply , and its climate resilience are up to par, in both the short and the long term. The Rhine Estuary-Drechtsteden region has drawn up a Preferential Strategy to that effect. The region has been working on the implementation of this strategy since 2014, within the framework set out by the Delta Decisions.
A number of dyke sections in the Rhine Estuary-Drechtsteden area do not meet the current standards. In recent years, a higher protection level has been agreed upon for most of the dykes, because of the increase in population and economic value behind the dykes. Furthermore, near dyke sections that are constructed on peat, subsidence causes additional tasking in terms of safety. In the longer run, the sea level rise and increasing river discharges ensuing from climate change will add to the flood risk management tasking. The rate at which this tasking is growing is not yet certain, but in the longer run, the rising sea level may have a major impact on the area. Climate change will also result in longer periods of drought, which will put additional pressure on the freshwater supply in the area. Finally, the region is faced with a spatial adaptation tasking.
Preferential Strategy for Flood Risk Management
At several locations, the elevation of the Rhine Estuary-Drechtsteden region is quite low. This means that several areas will be submersed very quickly and to a substantial depth in the event of a flood. Flood prevention is therefore of great importance.
In addition to 1) prevention, the Preferential Strategy for Flood Risk Management focuses on 2) pursuing sustainability in our country’s spatial planning, wherever possible, and 3) disaster control. In terms of prevention, we are consistently looking for the best combination of three types of preventative measures: storm surge barriers, dykes, and river widening. For example, with respect to the Hollandsche IJssel river, we are exploring the improvement of the Hollandsche IJsselkering storm surge barrier, as well as the coordination of pumping out polder water during storms.
In addition to limiting the flood risk, water-resilient spatial design adaptations are also being prepared. Disaster management requires additional attention in order to be prepared for evacuations, rescue operations, and restoration taskings in the event that things go wrong, nonetheless, in this complex and densely populated area.
A special feature of the Rhine Estuary-Drechtsteden region is the long stretches of areas outside the dykes which are densely populated and offer many employment opportunities. These areas are not protected by the dykes. The region is devoting additional attention to smart and resilient new developments, measures aimed at limiting loss, communication regarding the risks run by the residents and businesses, and options for creating shelter locations precisely in these areas in relation to (imminent) flooding in the event of dyke failure.
Finally, a long-term supra-regional system analysis will be scheduled, exploring multiple policy options for coping with the rising sea level. This study will cover issues such as dykes, areas outside the dykes, port accessibility, erosion, nature, shipping, and the freshwater supply. The study is expected to commence around 2040. The Delta Programme is monitoring new insights into climate change, flood risk management, and freshwater supply; if need be, the study will be launched at an earlier date.
Preferential Strategy for Freshwater Supply
For its freshwater supply, the western part of the Netherlands is dependent on a limited number of locations where fresh water from the rivers is let in (inlet points). The main inlet points are those near Gouda and Bernisse, which admit water to the Brielse Meer lake. In the future, these inlet points will become less reliable, because the water is increasingly salinising. At the same time, demand for fresh water is likely to increase. The freshwater supply to the western Netherlands will remain up to par by gradually expanding the emergency supply from the River Lek and the Amsterdam-Rijn canal.
One of the measures completed in 2018 involved the adaptation of the water inlet in the Prinses Irene locks. Several other measures were delayed or entail longer lead times. Such measures include the capacity expansion of the Central Netherlands Climate-proof Water Supply (KWA).
The freshwater supply from the Brielse Meer lake will gradually become more resilient: its management will be optimised in the near future. In addition, an improved monitoring system will be introduced, and near Spijkenisse an additional water inlet will be put into operation. The water manager will implement “smart water management” to reduce salinisation in the Hollandsche IJssel, the Amsterdam-Rijn canal, the Noordzee canal, and near the Hagestein weir. In addition, consumers need to economise in their use of water by capitalising on innovations.
The Rhine Estuary-Drechtsteden region is also working on climate resilience. These are some of the measures and projects:
- All the Working Regions in West-Netherlands have conducted stress tests in the fields of waterlogging, heat, and drought, covering virtually their entire territory. Several municipalities have also actively been working on flood impact reduction (Rotterdam, Dordrecht, Amsterdam), but this component is generally substantiated at a higher scale level (province of Zuid-Holland, Amsterdam Metropolitan Area, and Utrecht Security Region). Most of the regions embarked on risk dialogues in 2019, at the neighbourhood, city, or regional level.
- In the Rotterdam/The Hague Metropolitan Area Working Region, nearly half of the municipalities already have an adaptation strategy and/or spatial adaptation implementation agenda in place. A case in point is the Rotterdams Weerwoord Urgency Document, in which the municipality and the district water boards have elaborated how they will intensify their climate adaptation efforts in the years ahead.
- In the city of Dordrecht, experts, students, policy makers, and public and private party stakeholders have collectively elaborated pilot projects in the Dordtse Lenteschool.
- The city of Gouda is taking the lead in a national impact project, “Risk dialogue for a climate-proof subsiding historic city”.
- In Weerkrachtig Zuid-Holland, the province of Zuid-Holland sets out how it intends to climate-proof the province, in concert with its partners.
The western part of the Netherlands will see a great deal of new construction in the years ahead. The region is anticipating these projects by finalising the construction frameworks set out in the Zuid-Holland Climate-adaptive Construction covenant.
One of the components of the Preferential Strategy for flood risk management is an implementation agenda. Some of the measures featuring on this agenda:
- Alblasserwaard-Vijfheerenlanden study
In the Alblasserwaard-Vijfheerenlanden area, the district water board, the project developer, the municipality, and the province have signed a declaration of intent regarding a study into the possibility of combining a dyke improvement and an area development at the Mercon Kloos premises. The parties involved in this study have explored smart ways of combining spatial and economic developments in this area with raising and improving the dykes. In 2018, they presented a collective perspective memorandum, based on the three building blocks: Traffic on the Dykes, Quality of the Dykes and Embankments, and Multi-Layer Flood Risk Management.
- Eiland van Dordrecht study
In the second half of 2019, the city of Dordrecht will be conducting a process aimed at raising residents’ awareness of flood risks and of their own action perspectives. Several sessions will be organised to speak with residents. The Zuid-Holland Zuid Security Region will be using the results to draw up an evacuation plan for Eiland van Dordrecht in 2020.
- Strategic adaptation agenda for the area outside the dykes
In 2017, the municipality of Rotterdam drew up a strategic adaptation agenda for the area outside the dykes, in concert with the regional stakeholders. One of the follow-up actions is the development of area-specific flood risk management strategies for all the areas outside the dykes in this region. A pilot study has already produced such a strategy for the Botlek area.
- Disaster control
In the purview of the Water and Evacuation project, the Security Regions are mapping out the disaster control tasking. The city of Dordrecht has already drawn up a flood risk management plan as a pilot project; the Zuid-Holland Zuid Security Region has joined forces with other stakeholders to develop a similar plan for the Alblasserwaard-Vijfheerenlanden area. The Rotterdam-Rhine Estuary Security Region has conducted a case study to substantiate improvements in flood disaster management.
- Maeslant storm surge barrier
The Maeslant storm surge barrier plays a key role in protecting the area from flooding. Rijkswaterstaat has conducted a study into the reduction of the probability of failure and into the partial closure of the Maeslant storm surge barrier. The options for partial operation of the Maeslant storm surge barrier, such as closing one of the two sector doors, will serve as a back-up measure to stem a maximum of water when extreme weather necessitates closure of the barrier. In the period 2023-2028, Rijkswaterstaat will be conducting a follow-up study into the improvement of the Maeslant storm surge barrier. This study will focus on the implementation of measures and their effect on the flood protection of the hinterland.
- Voorne-Putten energy transition study
The Voorne-Putten Collaborative is examining the synergy between multi-layer flood risk management and the energy transition. The area covered by the study has been expanded from the Geuzenlinie (northern margin) to the entire island of Voorne-Putten.
- Hollandsche IJssel integrated approach
In 2018, Rijkswaterstaat and the Schieland en de Krimpenerwaard district water control board rolled out a study into further options to improve the Hollandsche IJssel storm surge barrier and their impact on the Hollandsche IJssel flood risk management tasking.
- River as a tidal park
The project focuses on softening and greening the – currently usually stony – embankments. In the years ahead, the programme will be expanded from Rotterdam to the Biesbosch nature reserve. Using natural processes is beneficial to nature development and recreation, and improves flood protection at a number of locations.
- Rhine-Meuse estuary study
At the request of the House of Representatives (Geurts motion), an additional study has been conducted into closing the Rhine-Meuse estuary on the seaward side, as a long-term option. This option involves locks in the Oude Maas and Nieuwe Maas, in combination with peak water storage in the Oosterschelde. The conclusion is that this alternative warrants a fully-fledged exploration when the study into replacement of the Maeslant storm surge barrier is launched (the study is expected to commence in 2040). The review of the Delta Decision is expected to result in the recommendation to conduct this study on the basis of a broad-based, supra-regional system analysis (see below). The Delta Programme is monitoring new insights relating to climate change, flood risk management, and freshwater supply; if need be, the study will commence at an earlier date.
Two pilots in the Rhine Estuary-Drechtsteden region have been awarded European Interreg grants. The grants were provided under European programmes focused on multi-layer flood risk management (FRAMES) and climate adaptation (BEGIN), in which the province of Zuid-Holland and the municipality of Dordrecht, respecti
Potential amendment of Delta Decision and Preferential Strategy
The Delta Decision on the Rhine-Meuse Delta has turned out to hold good until 2050. Currently, there is no reason for amending this Delta Decision. The line of approach to be taken in the Delta Decision covering the period beyond 2050 will mainly depend on the potential replacement of the storm surge barriers and the method to be used to this end. Another determining factor is the rate at which the sea level is rising. DP2017 has already indicated that the exploration of methods to replace the Maeslant storm surge barrier is expected to commence around 2040.
The review of the Delta Decision is expected to result in a recommendation to conduct this exploration on the basis of a comprehensive, supra-regional system analysis. This will generate a picture of multiple policy options, including, at any rate, variants involving a closable open barrier and closed barriers. A point of attention is that such a broader scope will add to the uncertainty regarding the future Preferential Strategy for the Rhine Estuary-Drechtsteden area. It is advisable to examine what this entails for the no-regret level of investments that are required in the near future, such as dyke improvement, freshwater supply measures, and investments in areas outside the dykes. The follow-up study into the improvement of the Maeslant storm surge barrier, which Rijkswaterstaat is conducting in consultation with the region, will also map out its impact on the hinterland. This will enable optimisation of the flood risk management tasking in the medium term.
The review will also cover the Preferential Strategy for the Rhine Estuary-Drechtsteden area. Potential amendments to this strategy will ensue from new insights that have been gained over the past five years in regional projects, a survey of the impact of a potentially accelerating and more extreme rise in sea level on this region, and an analysis of how major societal developments (such as the housing tasking and the energy transition) will impact the Preferential Strategy. In the years ahead, the evacuation strategies will also be finalised in more concrete terms.